One of the features of machine vision systems can be the ability to recognize a scene and identify features and objects in the scene. Machine vision systems can be used in portable devices, such as head-mounted devices, on industrial robots, driverless cars, and other devices. Over time, the performance of such systems can degrade. The degradation can be difficult to detect so long as the vision system is still generating a depth image. For example, it is difficult to determine whether the assigned depths are accurate.
Different types of depth camera technology exist. Time-of-flight (TOF) can be used to produce range images at any distance, but suffers from errors due to multipath and other factors. Active triangulation/structured illumination is less prone to multipath but is more sensitive to mechanical changes and misalignment caused by temperature changes, physical mistreatment, and such.
Standard structured light sensors are calibrated once at the factory under carefully controlled conditions when developed. The structured light sensors can suffer performance problems if either the pattern or optics change over time (e.g., due to physical shock) and need to be recalibrated in order to accurately measure distance.